1. Field of the Invention
The present invention relates to an electronically controlled throttle valve system adapted to actuate a throttle valve with an actuator such as an electric motor.
2. Description of Related Art
One of conventional systems of the above type is disclosed in Japanese Patent No. 3364873 for example. This system includes a throttle valve, an actuator for actuating the throttle valve, and a throttle body which houses and supports those throttle valve and actuator. An output-side end (base end) of the actuator is fixed to the throttle body through a support means. A non-output-side end (free end) of the actuator is supported to the throttle body through an elastic body. With such structure, both ends of the actuator are supported to the throttle body, thus effectively enhancing vibration resistance. The above patent mentions a coil spring, a wave washer, and an O-ring as examples of the elastic body.
In the electronically controlled throttle valve system mentioned above, however, the elastic body interposed between the actuator and the throttle body only has relatively small contact areas with the actuator and the throttle body respectively. Thus, contact pressure exerted on such small contact areas would be relatively large. Accordingly, in the case where the actuator has a metal case and the throttle body is made of resin, the resin throttle body tends to cause creep deformation. This may degrade the vibration resistance.